The present invention relates to an inductive radio control system for controlling a plurality of unmanned vehicles driven by an inductive radio apparatus along a predetermined route.
Unmanned vehicles are driven along predetermined routes in factories and the like to transport products. Current positions of vehicles are detected by a ground control unit, and the vehicles are controlled by a computer, a sequence controller or the like in accordance with the scheduled destinations thereof.
A data transmission unit is connected between the ground control unit and each vehicle. Operation instruction data is supplied from the control unit to each vehicle, and vehicle data is sent back from each vehicle to the control unit.
In this case, a conventional data transmission unit comprises an inductive radio apparatus. In the inductive radio apparatus, the transmitting antenna and the receiving antenna are inductively coupled to allow the data transmission/reception therebetween only when they are positioned extremely close to each other. A inductive trolley is arranged along the entire vehicle path to continuously exchange data between the control unit and the vehicles. However, it is difficult to provide the inductive trolley at switching points of the path and intersections with other vehicle paths or with conventional roads. For this reason, the inductive trolley must be divided at points of the path, railroad crossings or the like. When the inductive trolley is divided, a transmitter/receiver is required for each divided inductive trolley. In addition, in order to guarantee continuity of data exchange between the divided inductive trolleys, a proper method of installing the inductive trolley and a switching unit for data exchange between the respective divided inductive trolleys must be provided. When a vehicle path is complex, such a data transmission unit requires a complicated arrangement, resulting in high cost and impairing the reliability of the operation.
In order to detect a current vehicle position in the conventional system described above, a separate position sensor is required, or a travel distance is calculated by the number of revolutions of the wheel from the start point so as to estimate the current vehicle position. However, with the former method, total installation cost is increased. With the latter method, the degree of error is increased with an increase in distance, thereby degrading the precision of detecting a current vechicle position.
In order to solve the above problems, a plurality of loop antennas are separately arranged along the path and communication between the ground control unit and the vehicle is established every time when a vehicle passes a loop antenna. A stop instruction or a run instruction to a next loop antenna is supplied to the vehicle under a given loop antenna. These instructions are stored on a vehicle to control the operation of the vehicle. All the ground loop antennas are connected to a signal receiving means and all the vehicles run while transmitting signals. In this condition, the signals transmitted from the vehicle can be received by one of the ground loop antennas only when the vehicle comes to a position close to the ground loop antenna, causing induction in the ground loop antenna. Therefore, if one ground loop antenna receives a signal, this means that a vehicle has come into close proximity with the ground loop antenna. In this way, the position of each vehicle is detected.
In the data transmission unit described above, transmitters/receivers of an inductive radio apparatus are provided for the respective loop antennas. However, when the number of vehicles is small as compared with the number of loop antennas, numerous transmitters/receivers are required although the maximum number of actually operated units is the same as the number of vehicles, resulting in a high-cost, redundant system. In addition, in this system, when a failure occurs in a given transmitter/receiver, data transmission cannot be performed between the corresponding loop antenna and a passing vehicle so that the reliability of the system is degraded. Furthermore, when a loop antenna for a faulty transmitter/receiver is located at a stop position of a vehicle, entire system-down of an unmanned operation system occurs.